A milling cutter is a rotating disc with one or more cutting elements attached to its periphery that progressively removes stock as it traverses the workpiece beneath it. In a modular design of a milling cutter tool, the entities which make up a complete milling cutter assembly are treated as a unity, and include the body module to which all of the other modules are eventually attached or machined. In the body module is machined the mounting screw hole pattern, the drive module, the insert pocket module containing the insert, wedge, rest button, and screws, and the chip pocket module. Generally speaking, there are many different configurations of the body module in order to accommodate specific types of cutting inserts in order to achieve a certain cutting objective. In other words, the lead angle, the radial rake angle, and the axial rake angle of the cutter body design will vary as a function of the other module components which are utilized to form the milling cutter assembly.
The requirement for various different combinations of body modules, as well as the other modules of the assembly, in order to achieve a desired cutting instrument requires a large inventory of modular parts. It is an object of the subject invention to overcome this requirement for a large number of parts, and to provide a new and improved milling system having a single cutter body design. Preferably the latter has a zero to one degree lead angle, a zero degree radial rake, and a small axial rake angle, e.g., from minus one degree to plus five degrees. The single cutter body design may be employed with a plurality of different cutting inserts made according to the subject invention, to accommodate the axial, radial, and lead angles of a milling geometry, rather than the cutter insert being designed to accommodate the milling cutter body module.
Prior art milling cutters employed in the milling of difficult-to-machine materials, such as titanium 6AL-4V, at high metal removal rates normally machine at a rate of about 60 to 100 surface feet per minute (SFPM) and at a feed rate of 0.004 to 0.010 inches per tooth, even with the present state of the art tungsten carbide tools. Under normal machining practice, as the cutting edge wears and dulls the tool, the cutting insert is taken off after a certain predetermined period of time (based on the surface finish, the part size, the flank wear, the nose wear, and deformation of the cutting insert) or else, if further cutting is attempted, the cutting edge either breaks or burns out due to the force and temperature build-up. Furthermore, to allow the cutting edge to go to a later stage could result in a damaged workpiece part, damaged cutter, and thus is generally avoided. To prolong the life of the tool, present milling cutters are designed such that the cutting edges of the insert are indexed, and a fresh cutting edge is presented to the workpiece, and it has also been suggested to design the insert to reduce the length of the tool-chip contact, as well as controlling the length of the tool flank, as discussed in the publication Manufacturing Engineering, March 1980 at page 53.
In order to overcome the above mentioned shortcomings of prior art milling tools, it is an object of the subject invention to provide a cutting insert capable of machining difficult-to-machine materials, such as titanium 6AL-4V, at higher cutting speeds, e.g., four to six times the normal cutting speed (approximately 600 SFPM) with higher tool life. The subject invention could be applied to other materials, such as cast irons and steels and would provide the advantages of higher speed with reduced forces, thereby reducing the horsepower consumption for the same rate of material removal. Furthermore, machining time would be reduced, thereby resulting in high production rates, and with improved surface finishes.